Waste treatment apparatus and circulation unit therefor

ABSTRACT

In the activated sludge treatment of sewage and similar wastes the method of treatment involves the use of a tank in which sewage is mixed with previously activated sludge and subjected to the action of bacteria. Since oxygen is necessary for bacterial action, air distributing means are employed in such units. Herein a circulation and oxygenation cell is disposed in the aeration chamber adapted to draw floating material through the circulating unit from a plurality of zones at spaced points about the surface of the liquor.

United States Patent Fifer 1451 May 30, 1972 [54] WASTE TREATMENTAPPARATUS AND CIRCULATION UNIT THEREFOR [72] Inventor: Rolland L. Filer,P.O. Box 13175,

Louisville, Ky. 40213 [22] Filed: Feb. 18, 1971 21 App1.No.: 116,461

[52] US. Cl .....259/8, 259/97, 210/197 [51] Int. Cl. ..B0lt 7/22 '[58]Field ofSearch ..259/7,8,97,95;210/197, 210/195, 196

[56] References Cited UNITED STATES PATENTS v 2,889,047 6/1959 Coate..210/197 2,987,186 6/1961 Burgoon ..210/197 2,991,983 7/1961 Logan..259/97 3,053,390 9/1962 Wood ...210/195 3,235,232 2/1966 Conovcr..259/97 Primary Examiner-Robert W. Jenkins AttomeyNorman L. Wilson, Jr.

[ ABSTRACT 6 Claims, 4 Drawing Figures PATENTEDHAHO 1972 3, 666,242

sum 10F 2 INVENTOR ROLLAND L. F) FER HIS ATTORNEY PATENTED MAY 3 0 I972SHEET 2 OF 2 FIG. 2

FIG 3 INVENTOR ROLLAND L... PIPER M Hi5 ATTORNEY BACKGROUND OF THEINVENTION In the activated sludge treatment of sewage the method oftreatment involves the use of a tank in which sewage is mixed withpreviously activated sludge and subjected to the action of bacteria.This aerobic treatment is usually carried out in large tanks. Ordinarilythe rate of movement of sewage through the tank is low so that thesewage will remain in the tank a sufficient length of time to allow thebacteria to properly act upon the sewage. Since oxygen is necessary forbacterial action, air distributing means are employed, and these meansare usually so arranged as to make it possible for the sewage to receiveand absorb from the air as much oxygen as is necessary to support thebacterial action. In order to procure proper action it is also essentialto keep the body of sewage in substantially constant movement to avoidany settling or separating out of heavier or more solid particles.Aerobic treatment tanks must, then, be so constructed as to perform thefunctions of circulation and mixing continuously or intermittently for aperiod of time sufficient to purify the material so that the effluenttherefrom has a safe biological oxygen demand (B.O.D.). Treated liquidoverflows from the aerating tank into one or more settling or clarifyingtanks. In one type of aerating apparatus air or oxygen is introducedinto the aerating tank by means of an air diffuser line. In anotherapparatus an impeller is used to draw air into the liquid sludge as thesludge is agitated. This invention is concerned with aeration chambersof the impeller type.

Sewage or waste treatment apparatus of the type contemplated herein aredescribed in US. Pat. Nos. 3,053,390, 2,987,186 and 2,889,047. In US.Pat. No. 3,053,390 a shaft which carries an impeller on its bottom endshaft extends downwardly into the aeration chamber. The shaft issurrounded by a tube through which air is drawn by the impeller. Asecond tube, with its mouth opening into the aeration chamber near oneside terminates below the impeller. Circulation and aeration areachieved by air being drawn in above the impeller and liquid sludgebeing circulated through the tube ending below the impeller. Thedisadvantage of this apparatus is that sludge being returned through themouth of the tube is drawn off only at one point in the liquid level.This single sludge return does not effect complete circulation of sludgebeing aerated.

In US. Pat. Nos. 2,889,047 and 2,987,186 the impeller shaft issurrounded by an aeration tube which draws sludge as well as air inaround the shaft. In each instance the recirculating tube is formed witha funnel-like upper lip portion at the top of the circulating tube.Since the recirculating tube draws liquid sludge in at the center forcirculation, outer portions of the liquid sludge are not fullycirculated, and treated.

SUMMARY OF THE INVENTION In accordance with the practice of thisinvention a waste liquid or sewage treatment apparatus of the anaerobicdecomposition type is provided which efiects more complete circulationwithin the aeration tank. The unit not only draws liquor from theperiphery of the aeration chamber in effecting circulation, but alsomacerates incoming wastes or raw sewage thereby promoting bacterialaction. In the apparatus a circulation and oxygenation unit is disposedin about the center of the aeration chamber. This unit contemplates atubular waste inlet cell disposed in an upright position. The cell has aclosed top, and a plurality of ports in the upper portion thereof at thenormal liquid level to admit both recirculating waste liquid and airinto the cell. The bottom end of the cell is open, permitting flow ofwaste liquid from the cell into the bottom of the aeration chamber. Airliquid conduit means cooperate with the cell. Aeration and circulationare accomplished by the provision of a series of conduits the same sizeas each port, connected over each porthole thereby becoming integralwith the cell and extending radially outwardly perpendicular to the axisof the cell. An impeller is mounted within the cell in a lower portionof the cell above the open outlet. The impeller draws recirculatingwaste liquid and air first through the conduits and then down throughthe cell. An influent inlet opening is provided above the impeller tomacerate influent solids as they are drawn down through the cell.

DETAILED DESCRIPTION OF THE INVENTION This invention can perhaps bebetter understood by reference to specific embodiments described inconjunction with the accompanying drawings.

FIG. 1 is an isometric view of one sewage treatment plant embodying theinvention.

FIG. 2 is a top plan view of the apparatus shown in FIG. 1.

FIG. 3 is a sectional view of the same apparatus.

FIG. 4 is an isometric view showing a circulating and oxygenating unitwhich can be placed in any aeration chamber.

It isunderstood that auxiliary pipe lines, electric wire fittings andthe like have been omitted from the drawings. Since waste treatmentplants of the impeller type are known such details are within the skillof the art. It is the practice in units of this type to effectrecirculation by skimming ofl" floating sludge and flocculent material.This invention is based, in part, on the provision of a circulationinducing unit adapted to draw floating material through the circulatingunit from a plurality of zones at spaced points about the surface of theliquor. This is accomplished by means of tubes, or troughs 16.

A complete waste treatment plant 2, constructed of reinforced concreteor metal, depending on capacity, can be seen in FIG. 1. The apparatus isdivided into two compartments 4 and 6. However these can be separatevessels if desired. Compartment 4 is an aeration chamber containingliquor being subjected to biological action. The apparatus is operatedwith a constant amount liquor in aeration chamber 4 establishing a fixedliquid level or flow line shown in FIG. 3. The unit is sized based onuse so that liquor will remain in aeration chamber 4 for a period oftime sufficient for oxidation to take place. It then overflows wier 8into compartment 6 which is a clarification chamber provided withfillets 10. The apparatus thus operates in the usual and known manner.

In the aeration chamber oxygen must be provided for conversion andbacterial action. Additionally, a turbulent flow pattern must beeffected to maintain a circulation of liquor throughout the aerationtank so as to minimize quiescent zones and to prevent accumulation offloating unreacted solids on the liquor surface. Circulation andaeration herein are achieved by oxygenation unit 12. This unit is in theform of a tubular cell 14 provided near its top with radial ducts 16.Inside the cell an impeller is disposed near the lower end of the cellas shown in FIG. 4.

Referring now in greater detail to recirculation or oxygenation unit 12,this unit is disposed partly within aeration tank 4 as shown in FIG. 3and is operable to introduce air into the fluid waste material or sewagein the tank. The introduction of air is accomplished by impeller 18 seenin FIG. 4. This impeller can be driven from above or below. Desirablyhowever impeller 18 is secured to the lower end portion of drive shaft20 which is mounted within cell 14, usually along the vertical axisthereof. The drive shaft and hence impeller 18 are driven by a motor 22.This motor is mounted on platform 24 and is adapted to directly driveshaft 20. Desirably, in order to change impeller speed to bring in moreor less oxygen as desired, a belt and pulley wheel or other coupled orgeared drive means will be employed. In any event the actuation of motor22 will cause drive shaft 20 and hence impeller 18 to rotate at thedesired speed. The speed of rotation will depend upon the size of thecell, which in turn is based on the capacity of the treatment unit.Generally the impeller will rotate at a speed of 300 to 900 revolutionsper minute.

Blades of impeller 18 are so constructed that on rotation a downwardfluid surge through the cell is developed. The column of liquid and anyair within cell 14 above the impeller is thus forced downwardly towardthe floor of aeration chamber 4. An opening is provided in the top ofthe aeration chamber for the admission of air from outside the unit.Cell 14 terminates above the aeration chamber floor, or else the cell isprovided with passageways 26 through which circulating liquid moves outinto the aeration tank. The operation of impeller 18 in creating thesurge of fluid down through cell 14 also draws liquid from theperipheral portions of the waste liquid surface through ducts 16. Thisliquid and also air are drawn in through the portholes. Thus the outwardsurge of liquid beneath the cell, such as through openings 26, and theinward draw of liquid through ducts 16 create a flow pattern within thetank as shown by the arrows in FIG. 3.

As noted hereinbefore in addition to creating the flow pattern justdescribed, the impeller draws incoming sewage down through its bladesthereby serving as a maceration unit as well as a circulation unit. Aninfluent conduit 30 is connected to the cell at a point in itscircumferential surface beneath the radial ducts. The impeller 18 as aresult of its pitch, agitation and spin forces the raw sewage down andout into the aeration chamber along with aerated liquor.

It has been pointed out that the operation of sewage treatment plants inwhich this aeration and circulation unit will be employed will be of theconventional type similar to that described in US. Pat. Nos. 2,852,140,2,987,186 and others. The sewage remains in aeration chamber 4 whileoxidation and bacterial action take place as described hereinbefore. Thetreatment plant is operated at a constant liquid level, maintained byweir 8, at about the horizontal diameter of ducts 16. This level isshown in FIG. 3 as line 9, which is the top edge of weir 8. Thus a 500gallon unit has been operating very satisfactorily with a 4 foot longcell having a diameter of 14 inches containing a four-wing type 12 inchimpeller operating at 533 revolutions per minute. Compartment 6 acts asa clarifier for further purification of the waste liquid prior todisposal.

Several ramifications and modifications of this invention will occur tothose skilled in the art. For example aeration and circulation unit suchas 12 of FIG. 4 can be provided for existing sewage treatment plants,the unit replacing present aerating means. In addition aeration cell 14rather than having a circular cross section can have a polygonal crosssection such as a square, hexagonal or an octagonal cross section. Itwill be understood also that circulation unit 12 will be sized to fitthe particular aeration chamber in which it will be used. The overflowmust be such that the liquid level covers part but not all of the ductopenings. As indicated a 500 gallon unit contains a cell 14 which is 4feet high and has a diameter of 14 inches. In a 1,000 gallon treatingplant a l4 inch diameter cell would be 7 feet high. It can be seen toothat ducts 16 are shown to have open tops making them trough-like. Thereis no reason cylindrical conduits cannot be employed. Likewise openings26 in the base of the cell can assume any conformation, or the cell canbe suspended so that it terminates above the aeration chamber floor.Such variations are deemed to be within the scope of this invention.

What is claimed is:

1. In a waste treatment apparatus of the anaerobic decomposition typehaving aeration and clarification chambers formed by retaining walls,the combination of an aeration chamber with a circulation andoxygenation unit within the aeration chamber additionally maceratingincoming waste solids, the unit comprising a tubular waste inlet celldisposed in an upright position in about the center of the aerationchamber, said cell having a closed top, a plurality of ports in theupper portion thereof at the normal aeration chamber liquid level toadmit both recirculating waste liquid and air into said cell, and anopen outlet in its bottom end for flow of waste liquid into the bottomof the aeration chamber, airliquid conduit means integral with the cell,including a series of conduits, each the same size as a port, oneconduit being connected over each porthole virtually perpendicular tothe axis of the cell, extending radially outwardly from the cell to apoint close to the walls of the aeration chamber in such a manner thatwaste liquid passing through the ports must pass through said connectingconduits, an impeller mounted within said cell in a lower portionthereof above the open outlet, the blades of said impeller being soadapted that waste liquid is drawn down through the cell, an influentinlet opening into said cell at a point above the impeller, mechanicalmeans for driving the impeller to macerate influent solids in the cell,to draw air and circulating liquor through the connecting conduits anddown through the cell, and to eject the waste liquid through the cellopen outlet.

2. The apparatus of claim 1 wherein the conduits connected to theportholes are cylindrical tubes enclosing said portholes.

3. The apparatus of claim 1 wherein the conduits connected to theportholes are troughs enclosing the bottom halves of said portholes.

4. The apparatus of claim 1 wherein the aeration chamber has a squarecross section, wherein the cell has four ports, wherein the conduitscovering the ports extend to the four corners terminating a few inchestherefrom and wherein the mechanical drive means includes a motorcoupled to a shaft extending down into the cell.

5. The apparatus of claim 1 wherein the aeration chamber is cylindricaland wherein the cell in the center thereof has more than 4 ports andconduits covering said ports.

6. The circulation and oxygenation unit of claim 1.

1. In a waste treatment apparatus of the anaerobic decomposition typehaving aeration and clarification chambers formed by retaining walls,the combination of an aeration chamber with a circulation andoxygenation unit within the aeration chamber additionally maceratingincoming waste solids, the unit comprising a tubular waste inlet celldisposed in an upright position in about the center of the aerationchamber, said cell having a closed top, a plurality of ports in theupper portion thereof at the normal aeration chamber liquid level toadmit both recirculating waste liquid and air into said cell, and anopen outlet in its bottom end for flow of waste liquid into the bottomof the aeration chamber, air-liquid conduit means integral with thecell, including a series of conduits, each the same size as a port, oneconduit being connected over each porthole virtually perpendicular tothe axis of the cell, extending radially outwardly from the cell to apoint close to the walls of the aeration chamber in such a manner thatwaste liquid passing through the ports must pass through said connectingconduits, an impeller mounted within said cell in a lower portionthereof above the open outlet, the blades of said impeller being soadapted that waste liquid is drawn down through the cell, an influentinlet opening into said cell at a point above the impeller, mechanicalmeans for driving the impeller to macerate influent solids in the cell,to draw air and circulating liquor through the connecting conduits anddown through the cell, and to eject the waste liquid through the cellopen outlet.
 2. The apparatus of claim 1 wherein the conduits connectedto the portholes are cylindrical tubes enclosing said portholes.
 3. Theapparatus of claim 1 wherein the conduits connected to the portholes aretroughs enclosing the bottom halves of said portholes.
 4. The apparatusof claim 1 wherein the aeration chamber has a square cross section,wherein the cell has four ports, wherein the conduits covering the portsextend to the four corners terminating a few inches therefrom andwherein the mechanical drive means includes a motor coupled to a shaftextending down into the cell.
 5. The apparatus of claim 1 wherein theaeration chamber is cylindrical and wherein the cell in the centerthereof has more than 4 ports and conduits covering said ports.
 6. Thecirculation and oxygenation unit of claim 1.